Production of sheet and strip



June 15, 1954 w. c. F. HESSENBERG ET AL 2,680,978

PRODUCTION OF .SHEET AND STRIP Filed July 5, 1951 2 Sheets-Sheet l Fafiol H502 Filed July 3, 1951 June 15, 1954 w. c. F. HESSENBERG ET AL 2,680,978

PRODUCTION OF SHEET AND STRIP 2 Sheets-Sheet 2 2e ,VOLTAGE 9 ADJUSTER STABILISER AMPLIFIER AMPLIFIER AND 3/ 30 AND oenooumoa osnoouunoa W 32 fi a I E L lnventbrs:

Afforneya Patented June 15, 1954 V 2',sso,97s= v PRODUCTION OF SHEET AND STRIP Wilfrid Cecil Frederick Hessenberg, and Raymond Bernard Sims, Sh land; assi'gnors to The British. Iron Research. Association, London,

British company Bromley; id; Engandsteels. England; a-

Applicationluly 3;,1951, Serial No; 234,982

Claims priority, application Great: Britain July 5, 1950 7 Claims. 1.

The present inventionrelatesto theproduction of sheet or strip by'rolling or by drawing through dies of the kind. having opposing die surfaces Whose separation is adjustable.

In such production. the material entering between the rolls orv opposing, die surfaces may vary in thickness and other properties along its length and across its width asthe result oi'previous.v treatment. In known rolling or drawing processes; these thickness. variations are not entirely removed, and in fact other variations may beimposed' by'changesin the conditions of rolling or drawing.

At present the usual'm'ethod of controlling the thickness of such: sheet or strip issuing from a rolling mill'is-to' measure continuously the thickness by means of a contact micrometer as the material emerges from the. rolls, and manually to control the, power operated roll screws to adjust the distance between the rolls whenever a consistent departure from the desired thickness is indicated; Generally the micrometer is placed some distance from the exit side of, the rolls. so that anindication of a change in thickness is not manifest until some" time. after the material has passed through the rolls. There is then a further delay whilstthe operator becomes aware of the change and prepares'to-make an adjustment to the position of therolls; Whilst making this adjustment the operator may quite likely over-correct with the result that the thickness is likely to vary about a mean value: A substan'- tial length of off-gauge strip may thuspassthrough the mill.

One object of the present invention is' to provide a new or improved method of controlling the thickness of'the sheet or'strip produced.

This new-orimproved method is based on the following facts; For-convenience these facts and the description hereafter will be explained in relation to thepassage of metal strip between rolls, but it will be readilyapparent that they are equally applicableto strip of materials other thanmetal, to sheet of any suitable material, andto drawing through dies of the kind specified above.

The method of controlling the thickness of the strip in th present invention is dependent upona relationship'between the separating force between the rolls engenderedby'the-strip passing througlr them, the roll setting, which is defined as theminimum distancebetween the rolls when no separating force is acting, and of the outgo ing or issuing thickness. This relationship states that the separating force is proportional to the difference between: the outgoingstripthickness and the roll setting: The factor of 'proportion ality is the elastic constant of the-mill commonly known as the mill spring; A- corollary of this relationship is thatiianyincrease separating- 2 force is accompaniedby a decrease in roll" setting. equal to the change in separating force divided. by the mill spring, the outgoing strip thickness will remain constant; Similarly; to maintain the.

the roll adjusting mechanisms; which act on the; two ends of the roll and thus ensure that the thickness of" the twoedges of the ship" remain equal to one another: In" this way uniformity of. gauge is continuously preserved both' alongjand across the strip.

When applied to-the production of metal sheet or strip; the rolling, or drawing can be effected when themetal is in either the hot or' cold state:

In carrying out the invention load responsive elements which will respond to vari'ationsin thev separating force are incorporated in the mil-l and linked by mechanical, electrical and /or' hydrau-licr means with the roll adjusting mechanisms in such: a way that the desired relationship between the: changes in separating force and rollsetting is continuously maintained;

One formof apparatus by which thepresent invention may be performed will now be d escribed, by way of" example only; with reference to the accompanying diagrammatic drawings; in which--- 7 Figure 1- isa sectional side view of a rolling; mill" arranged for the performance-of the inveni-- tion, whilst Figure 2 is an end view of the rolling-'mil-l shown in- Figure 1-, and

Figure 3- isa side view' of" a rolldisplacement..- meter which is responsive to the changes the rollsetting,

Figure 4 is r aschematic drawing: of the control; arrangement for the apparatus,

Figure 5 is a v-iew similarto Figure-q cfia.form of mill using. dies of. the kind referred to'abova; andwhich may beused with the control arrange mentin place of the rolling mill-.

Referring now to the" drawings, Figures 1. and 2 show a rolling millsomewhat; similarc to: conventional mills used: for the rolling of steel? and comprising'work rolls l0 supported-in upper and lower bearing: chock-s: H amp M respectively-*- which' are themselves mountedin: a; mill l st'andi.

13. The mill is, howevenmodified from conventional form by the replacement of the normal manually-operated roll adjusting screws by fluid-operated rams [4 operating in cylinders 15. The free end of each ram [4 bears on a meters !8 one of which is mounted between the top of each of the upper chocks H and the underside of the top of the frame 13. As shown in detail in Figure 3, each meter l8 comprises a sliding rod I9 which passes through the base of a housing and carries a cone 2! at its upper end. The rod I9 is preferably of a metal having a very low coeificient of thermal expansion. Two cantilever arms 22 are attached by one end to the top of the housing with their free ends in contact with the surface of the cone 2|. The cantilever arms 22 carry electrical resistance strain gauges 23, which are arranged so that any flexing of the arms 22 due to movement of the rod l9 causes a change in the resistance of the gauges 23. The housing 20 is enclosed in a water cooling jacket 24. Thus variations in the distance between the ends of the rolls at which the particular meter is mounted causes a change in the resistance of the gauges 23.

Referring now to Figure 4, each strain gauge I1 is incorporated in a temperature compensated Wheatstone bridge network (see British Patent No..626,206) whilst the strain gauges 23 are incorporated in a similar network 26. Both networks 25 and 26 are supplied with alternating current at a frequency of 500 cycles per second from a source 21. The supply to network 25 is derived via a stabiliser 28 which ensures a substantially constant voltage input to the network 25 whilst the supply to network 26 is supplied via a voltage adjuster 23. The outputs from the bridges 25 and 26 are fed respectively to combined amplifiers and demodulators 30, 31 whose direct current outputs are combined in opposition and applied to a coil 32. It will be understood that the outputs of the networks 26 and 25 will be dependent upon the roll setting and the separating force. The voltage input to network 26 and the gain of amplifiers 30, 3| are adjusted so that with the desired outgoing thickness of material the outputs from demodulators 33, iii are equal so that the voltage across the coil 32 is zero. Any change in separating force occasioned by a variation in outgoing thickness from the desired value will result in an out-of-balance voltage in the. coil 32.

The coil 32 is wound on a core 33 and is movable within a polarising field provided by a permanent magnet 34 against the pressure of return springs 46. The core 33 is attached to the piston 35 of a diflerential fluid valve 36 which controls the supply of low-pressure fluid from an input 31 to one side or the other of a double acting piston 38 in normal manner. The pressure acting on piston 38 is modified by a fluid intensifier 39 which is connected by pipe 40 to the rams Hi. The intensifier acts'so'that the pressure of the piston 38 is amplified when ,1 increasing pressure is required to be applied to the rams 14 for adjusting the roll setting,

whilst a reduction in pressure in the intensifier 39 is obtained when. the piston 38 moves in the opposite direction. Thus an out-of-balance voltage in the coil 32 causes a movement of the piston 35, the direction of movement being dependent upon the polarity of the out-oi-balance voltage which is itself dependent upon whether the thickness has'increased or decreased. Movernent of the piston 35 in turn produces a change in the roll setting which is in such a sense as to modify the output from network 25 and reduce the out-of-balance voltage to zero. In this manner the desired relationship between separating force and roll setting is, substantially maintained.

Figure 5 shows a die stand 4! which can be used in a similar manner to the mill of Figure 1. The die stand 4| comprises upper and lower lips 42, 43 respectively, which may for example be of steel or metal carbide. The lower lip 43 is supported in a holder block A l which is fixed relative to the die stand 41. whilstthe upper lip 42 is carried by a holder block 45 so as to be movable relative to the other lip 43 for adjustment of the die setting (which corresponds to the roll setting in the case of the rolling mill)'. The die stand includes fluid operated rams Hi operating in cylinders [5, an interposed cylindrical member l6 carrying electrical strain gauges ll and meters l8, all similar to those already described in conjunction with the rolling mill of Figures 1 and 2. The control arrangement is also similar to that described in connection with Figures 1 to 4, and further description is thought to be unnecessary.

Although in the above described arrangements the various meters have been arranged to produce electrical signals varying in accordance with variations in the separating force and the roll (die) settings, which then effect control by fluid means, it will be understood that alternatively the control may be effected by mechanical or fluid means alone or by combinations of these together and/or with electrical means.

It will be appreciated that in contrast to the normal existing method referred to above the monitoring of the thickness of the material is eliectcd whilst it is in the roll or die gap, and correction is made with only the time delay inherent in the control mechanism.

We claim:

1. In apparatus for reducing the thickness of material, a thickness reducing member having opposed material engaging surfaces between which a separating force is established by the passage of material therethrough, means for adjusting the 3 separation between said opposed material engaging surfaces in response to a control signal, means for continuously developing a first signal proportional to the separating force, means for continuously developing a second signal proportional to the separation between said opposed surfaces, and means for combining said first and second signals in predetermined proportions to give said control signal.

2. In apparatus for reducing the thickness of material, a thickness reducing member having opposed material 7 engaging surfaces between which a separating force is established by the passage of material therethrough, control signal responsive means for adjusting the separation between said opposed material engaging surfaces, means for developing a signal whose amplitude varies in correspondence to changes in said separating force, means for developing a further signal whose amplitude varies in correspondence to changes in said separation, variable gain signal amplifying means for amplifying said first mentioned signal and said further signal in different proportions, signal combining means for combining said first mentioned signal and said further signal after amplification, to give an output signal, and means for applying said output signal to said control signal responsive means.

3. Apparatus according to claim 2, in which the signal combining means comprises means for balancing the first mentioned signal against the further signal, and the relative gain of the signal amplifying means in respect of the two signals is such that said output signal is zero when the material leaving the apparatus is of predetermined thickness.

4, In apparatus for reducing the thickness of material, a thickness reducing member having opposed material engaging surfaces between which a separating force is established by the passage of material therethrough, control signal responsive means for adjusting the separation between said opposed material engaging surfaces, means for developing a signal whose amplitude is proportional to said separating force, means for developing a further signal whose amplitude is proportional to said separation, variable gain amplifying means for amplifying said further signal by a predetermined amount, further variable gain amplifying means for amplifying said first mentioned signal by an amount equal to a predetermined fraction of said predetermined amount, means for developing a control signal which is proportional to the difference between the amplified first mentioned signal and the amplified further signal, said control signal having a predetermined value when the material leaving the apparatus is of predetermined thickness, and means for applying said control signal to said control signal responsive means.

5. In apparatus according to claim 4, a supporting stand in which said thickness reducing member is mounted, and wherein said means for developing said further signal comprises a stress responsive member interposed between one of said opposed material engaging surfaces and said stand, an electrical resistance strain gauge mounted on said stress responsive member and responsive to variations in the stress applied to said stress responsive member, and means for applying an electric potential to said strain gauge, the resultant electric current through said strain gauge providing said further signal.

6. In apparatus according to claim 4, a supporting stand in which said thickness reducing member is mounted, and means for movably supporting at least one of said opposed material engaging surfaces in said stand, the relative position of said last mentioned means in said stand being determined by said control signal responsive means, and wherein said means for developing the first mentioned signal comprises a stress responsive member interposed between said stand and said means for movably supporting the one of said opposed material engaging surfaces, an electrical resistance strain gauge mounted on said stress responsive member and responsive to variations in the stress applied to said stress responsive member, and means for applying an electric potential to said strain gauge, the resultant electric current through said strain gauge providing said first mentioned signal.

7. In a rolling mill for reducing the thickness of material passing between a pair of work rolls, a supporting stand, one of said work rolls being fixed relative to said supporting stand and the other being movable relative to said supporting stand, a pair of chocks each housing one end respectively of the movable work roll, two members movably mounted in said stand and each adapted to apply pressure to one of said pair of chocks respectively whereby said movable work roll is urged towards the other work roll, electrically operated means for effecting movement of each of said movable members independently, two stress responsive members each interposed between one of said chocks and one of said movable members, two electrical resistance strain gauges each mounted on one of said stress responsive members, means for applying an electric potential to each of said strain gauges whereby the changes in current through each strain gauge is proportional to the variations in the separating force engendered between the work rolls at the corresponding end thereof by the passage of material through said work rolls, two further stress responsive members each interposed between one of said chocks and said supporting stand, two further electrical resistance strain gauges each mounted on one of said further stress responsive members, means for applying an electric potential to each of said further electrical resistance strain gauges whereby the changes in current through each of said further strain gauges is proportional to the variations in the distance between the corresponding ends of the work rolls, means for amplifying the changes of each of the currents through the strain gauges, the currents through said further strain gauges being amplified to a difierent degree from the currents through said first mentioned strain gauges, means for producing two control currents by combining in opposition each of the amplified currents from said further strain gauges with the amplified current from that one of the first mentioned strain gauges which is located at the corresponding end of said work roll respectively and means for applying each of the control currents to said electrically operated means for effecting movement of that movable member operating upon the corresponding end of the work roll.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,669,550 Biggert, Jr May 15, 1928 2,152,556 Messinger Mar. 28, 1939 2,180,176 Stone Nov. 14, 1939 2,267,380 Tyler Dec. 23, 1941 2,276,816 Bagno Mar. 17, 1942 2,276,817 Bagno Mar. 1'7, 1942 2,276,843 Hathaway Mar. 1'7, 1942 2,323,267 Wittkuhns et al. June 29, 1943 2,332,288 Zeitlin Oct. 19, 1943 2,336,371 Shayne et a1 Dec. 7, 1943 2,342,374 Shayne et a1 Feb. 22, 1944 2,345,931 Gates Apr. 4, 1944 FOREIGN PATENTS Number Country Date 644,957 Germany May 19, 1937 664,993 Germany Sept. 10, 1938 

